1. Field of the Invention
The present invention relates to a joint for joining hydrogen gas running route-forming members and a portable hydrogen flame ionization gas detector, in which a hydrogen gas running route is formed by means of this joint for joining hydrogen gas running route-forming members.
2. Description of the Background Art
As a method for detecting a concentration of, for example, a hydrocarbon gas, has heretofore been used, for example, a system that gaseous molecules of the hydrocarbon gas are ionized in a hydrogen flame to detect an ionic current, and the concentration of the hydrocarbon gas is detected on the basis of the result of the detection of the ionic current.
As hydrogen flame ionization gas detectors making good use of such a detection system, have been proposed those of various structures (see, for example, Japanese Patent Application Laid-Open No. 2000-227416), and portable gas detectors are used in tests for gas leakage from, for example, conduits and supply pipes buried in the ground.
In a portable hydrogen flame ionization gas detector, it is necessary to arrange all necessary component members within a limited space in a case for the detector making up the hydrogen flame ionization gas detector, and it is thus substantially difficult to form a whole hydrogen gas running route from a hydrogen gas supply source to a sensor part by one pipe member. Accordingly, under the circumstances, a plurality of hydrogen gas running route-forming members are joined with a joint or joints to arrange a pipeline, thereby forming a hydrogen gas running route.
However, the joint used in the formation of the hydrogen gas running route desirably has a structure that at least one hydrogen gas running route-forming member is removably joined to the joint from the reasons of, for example, the necessity of maintenance.
As such a joining method is generally often used, for example, a method in which a gas running route-forming member is screwed into a joint. Since the atom of hydrogen gas is extremely small, however, the hydrogen gas may be leaked from the joined portion by the screwing when hydrogen gas runs. As a result, there is a risk of causing firing, explosion or the like.
In order to solve such a problem, a measure for preventing the leakage of the hydrogen gas from the joined portion has been taken in conventional joints for joining hydrogen gas running route-forming members.
However, such a joint is generally liable to become large in size and hence hard to use for forming a hydrogen gas running route in a portable hydrogen flame ionization gas detector and involves a possibility that the whole gas detector may become enlarged.